The cracking behavior of bitumen has attracted widespread attention worldwide because fatigue cracks are recognized as the cause of bitumen cohesive failure under fatigue loads. However, cracking is not the only type of damage that occurs during the fatigue process. This study aims to gain a deeper understanding of the fatigue damage mechanism of bitumen. In this study, four types of bitumen were subjected to time sweep test with various stress amplitudes. Rheological properties of test samples were collected during the time sweep test. The surface of the fatigue failed sample was photographed as the cohesive failure appearance. These failure appearances showed both the conventional factory roof morphology and the wave-shaped pattern. Factory roof morphology was related to the cracking of the asphalt binder, and the wave-shaped pattern was linked to the plastic flow of the asphalt binder. This proved that two types of damage occurred in asphalt binder under repeated shearing: cracking and plastic flow. The former and the latter one respectively dominated the failure process of asphalt binder under small- and large-amplitude fatigue loads. In addition, it was found that the profile of the failure surface was concave rather than horizontal, which proved the non-negligible effect of normal force on the cracking behavior of the asphalt binder.                                                  

Understanding the Cohesive Failure Mechanism of Bitumen Under Repeated Shearing

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